Thermionic valves



T. W. MYFORD THERMIONIC VALVES Sept. 6, 1960 2,951,958

Filed April 30. 1959 IIIVEIITOR THOMAS WILLIAM I'IYFORD United States Patent THERMIONIC VALVES Thomas William Myford, Enfield, England, assignor to Siemens Edison Swan Limited, London, England, a British company Filed Apr. '30, 1959, Ser. No. 810,048

Claims priority, application Great Britain May 5, 1958 '3 Claims. (Cl. 313-1) tionship relative to the envelope and a subsidiary electrode assembly which has a shorter axial length than the main electrode assembly and has a support comprising an insulating strip secured to the main electrode assembly.

The insulating strip may be areuate in shape and the ends of the arc can be secured to flanges provided in the main electrode assembly.

In one embodiment a screen is provided secured to the main electrode assembly and positioned so as to be interposed between the two electrode assemblies. The ends of the insulating strip can be attached to the screen.

In order that the invention may be more fully understood reference will now be made to the accompanying drawing, in which Fig. 1 and Fig. 2 show alternativeembodiments of the invention.

Referring now to Fig. 1 there is shown therein a main electrode assembly 1 having means for being held in rigid spaced relationship relative to an envelope (not shown) which means comprises two mica discs 2 and 3 mounted at either end of assembly 1 the peripheries of which contact the envelope of the valve. A subsidiary electrode assembly 4 is also provided within the envelope side by side with assembly 1. In prior art arrangements assembly 4 was held between discs 2 and 3 in like manner to assembly 1. However, since assembly 4 is normally of smaller diameter to assembly 1 this resulted in a rather elongated and weak structure.

In accordance with the invention therefore assembly 4 has a shorter axial length than assembly 1. The supports for assembly 4 comprise the lower insulating disc 3 on the one hand and an insulatingmica strip 5 of arcuate shape on the other hand which is secured to the main electrode assembly by means of tags 6 welded at either end of the strip. These tags are welded to the flanges 7 which normally form part of the anode of assembly 1. A plurality of pips or snubbers 10 are provided on the internal face of the mica strip 5 to space the strip from the anode and prevent excessive heating of the mica.

2,951,958 Patented Sept. 6, 1960 It will thus be seen that since assembly 4 is of shorter length it will be more rigid and the power requirements of the cathode heater of assembly 4 will be smaller than if the assembly was of equal length to assembly 1.

An alternative embodiment is shown in Fig. 2 in which like parts have like reference numerals.

In this embodiment a screen 7 is interposed between the two assemblies, which screen is connected to an earthing pin of the valve. Insulating strip 5 is secured at its ends to screen 7 by means of flanges 8 on the screen being bent back at right angles so as to support strip 5, and tabs 9 integral with flanges 8 are inserted in corresponding slots in strip 5. Thus with this arrangement no additional welding is required.

Also the pips or snubbers shown in the Fig. 1 embodiment are not required as the arcuate mica strip contacts shield 7 which is at a much lower temperature than the anode.

What I claim is:

l. A thermionic valve comprising an envelope containing a main electrode assembly, support means positioned at either end of the assembly for holding said assembly in rigid spaced relationship relative to the envelope, a subsidiary electrode assembly which has a shorter axial length than the main electrode assembly and is supported side by side to said main electrode assembly, and an insulating strip secured to the main electrode assembly which strip supports one end of said subsidiary electrode assembly, the other end of said subsidiary electrode assembly being supported by one of said support means.

2. A thermionic valve comprising an envelope containing a main electrode assembly, a pair of insulating discs to which the ends of the main electrode assembly are secured, which discs serve to hold said assembly in rigid spaced relationship relative to the envelope, a subsidiary electrode assembly having a shorter axial length than the main electrode assembly and extending side by side to said main electrode assembly, an insulating strip secured to the main electrode assembly, said subsidiary electrode assembly being secured at one of its ends to one of said insulating discs and at its other end to said insulating strip.

3. A thermionic valve comprising an envelope containing a main electrode assembly, means positioned at either end of the assembly for holding said assembly in rigid spaced relationship relative to the envelope, a subsidiary electrode assembly which has a shorter axial length than the main electrode assembly, and extends side by side to said main electrode assembly, an insulating strip secured to the main electrode assembly which strip supports one end of said subsidiary electrode assembly, the other end of said subsidiary electrode assembly being supported by one of said insulating discs, and a screen interposed between said main electrode assembly and said subsidiary electrode assembly.

References Cited in the file of this patent UNITED STATES PATENTS 2,253,208 Miller Aug. 19, 1941 FOREIGN PATENTS 642,112 Great Britain Aug. 30, 1950 

